This invention relates to epoxide-based photocurable compositions and to processes for preparing these compositions. More particularly this invention relates to polyacrylate- or methacrylate-containing photocurable monomers which are of relatively low viscosity and yet possess a cure response equivalent to other epoxide-based photocurable monomers.
For many years it has been known to prepare polyacrylic- or methacrylic-based monomers by reacting acrylic or methacrylic acid with a polyglycidyl ether, such as the diglycidyl ether of Bisphenol A. Examples of patents which involve the use of these compositions in photocurable systems include U.S. Pat. Nos. 4,072,592; 3,676,398 and 3,770,602. In addition, in at least one instance in the prior art, a polyglycidyl ether has been reacted with a polyol or a polyol ether and the resulting product reacted with acrylic acid or methacrylic acid. See U.S. Pat. No. 2,890,202, issued June 9, 1959. However, the product disclosed in this patent is not shown to be useful as a photocurable monomer.
The polyacrylic or methacrylic esters of polyglycidyl ethers have been particularly useful in protective coatings because of their rapid cure rates, high degree of toughness and good chemical resistance. However, their extremely high, neat viscosity has been a serious drawback, particularly in those photocurable systems where the presence of a solvent would significantly reduce the cure time of the system. Because nearly all acrylic or methacrylic esters of polyglycidyl ethers are resinous and of extremely high viscosity, often approaching 5,000,000 cps, it is virtually impossible to use these materials without at least employing some solvent or diluent.
Thus, it is an object of this invention to prepare photocurable monomers which are acrylate or methacrylate esters of polyglycidyl-containing compounds.
It is another object of this invention to prepare such acrylic or methacrylic esters having viscosities sufficiently low to allow their use in essentially 100% solids photocurable systems without the necessity of employing diluents or solvents.
It is another object of this invention to prepare photocurable compositions which are of low viscosity, but at the same time maintain the relatively high degree of cure rate present in prior art acrylic or methacrylic esters of polyglycidyl ethers.
These and other objectives are obtained by preparing the compositions of the instant invention.